發炎性肌肉病變抗體分群在肌炎相關疾病之臨床應用

Clinical utility of myositis antibody clustering by line-blot assay in patients with myositis-spectrum disorders

目的：研究肌炎抗體在肌炎相關疾病患者之表現，以及評估抗體樣態與臨床表徵之關聯。方法：本回溯性研究中，回顧肌炎相關疾病患者以免疫墨點染色檢驗法接受肌炎抗體檢測，並且對照病患之器官侵犯與臨床表現，分析免疫墨點染色檢驗法之臨床關聯性與對於診斷之價值。結果：自2006至2022年，共收入189位發炎性肌肉病變（82位皮肌炎、49位多發性肌炎、14位免疫引起壞死性肌炎、7位重疊症候群）及免疫相關間質性肺炎患者進入分析。其中有140位（74％）病患為肌炎特異性抗體陽性、28位（15％）病患肌炎相關抗體陽性。具有肌炎特異性抗體之病患與皮膚、肌肉、及肺部表現有正相關。相對於抗體陰性的個案，抗MDA-5抗體與較低的肌肉酵素升高（14％ vs. 62％，p＝0.001）相關、但是與皮膚侵犯（86％ vs. 57％，p＝0.04）、mechanic's hand（43％ vs. 0％，p＝0.001）、與間質性肺炎（90％ vs. 24％，p＜0.001）呈正相關。抗合成酶抗體則與較少的皮肌炎及較多的間質性肺炎（73％ vs. 24％，p＜0.001）相關。超過一個抗體陽性的病患與間質性肺炎（75％ vs. 24％，p＝0.014）相關。結論：在臺灣的肌炎相關疾病族群，肌炎抗體檢測或可提供臨表現辨認與重要器官影響之分類依據。

Objective: To study the prevalence of myositis antibodies in patients with myositis-spectrum disorders, and to evaluate the clinical correlation between the antibody profile and the clinical manifestations. Methods: We retrospectively collected patients of suspected myositis and related disorders who underwent immunoblotting assays of myositis-specific and associated antibodies. The clinical characteristics and organs of involvements were recorded. Finally, we analyzed the clinical correlation and diagnostic value of the myositis antibody assay in diagnosing and classifying myositis-related disorders. Results: From 2006 to 2022, 189 patients with idiopathic inflammatory myopathies (82 dermatomyositis, 49 polymyositis, 14 immune-mediated necrotizing myopathies, and 7 overlap syndromes) and interstitial pneumonia with autoimmune features were included in the analysis. The myositis-specific antibody was found in 140 (74%) patients and myositis-associated antibody in 28 (15%) patients. The presence of specific antibodies was associated with occurrence of the skin, muscle, and lung manifestations. The anti-melanoma differentiation-associated protein 5 antibody (anti-MDA5) was associated with less creatine kinase elevation (14% vs. 62%, p=0.001), but with increased overall skin involvement (86% vs. 57%, p=0.04), mechanic's hand (43% vs. 0%, p=0.001), and interstitial lung disease (90% vs. 24%, p ＜ 0.001). The anti-synthetase antibodies other than anti-MDA5 was associated with less dermatomyositis-specific skin manifestations and more interstitial lung disease (73% vs. 24%, p ＜ 0.001). The positivity of multiple antibodies was associated with interstitial lung disease (75% vs. 24%, p=0.014). Conclusions: In patients with myositis-spectrum disorders, the myositis antibody testing might indicate the clinical phenotypes and organ involvements in Taiwanese population.